Freezer and refrigerator provided with freezer

ABSTRACT

Respective evaporators are set to a proper value in evaporation temperature and the efficiency in refrigeration cycle is enhanced, resulting in a reduction of energy consumption. A refrigerating unit and a refrigerator comprise a compressor, a condenser, a plurality of evaporators connected in series, a refrigerant flow rate adjustable unit and a refrigerant, thereby constituting a refrigeration cycle. The refrigerant flow rate adjustable unit controls each respective evaporation temperature of the plurality of evaporators. Preferably, the refrigeration unit further comprises a bypass circuit bypassing at least one of the plurality of evaporators and, when needs arise, the refrigerant is channeled through the bypass circuit. The refrigerant flow rate adjustable unit controls a flow rate of the refrigerant such that an evaporation temperature of the respective evaporators located at the upstream side of the refrigeration cycle is made higher than an evaporation temperature of the respective evaporators located at the downstream side thereof.

TECHNICAL FIELD

The present invention relates to a refrigerating unit and a refrigeratorequipped with the refrigerating unit.

BACKGROUND ART

In recent years, a refrigerating unit to provide cooling for a pluralityof compartments, each provided with an evaporator, and a refrigeratorequipped with the refrigerating unit have been disclosed.

A prior art refrigerating unit of this kind is disclosed in the JapanesePatent Application Unexamined Publication No. S58-219366 of 1984.

Next, a description is given to the aforementioned prior artrefrigerating unit with reference to drawings.

FIG. 9 is a block diagram of a cooling system of the prior artrefrigerating unit. In FIG. 9, a refrigerant compressed in a compressor1 is condensed by dissipating heats in condenser 2 and then fed torefrigerant branching unit 3.

The branched refrigerant is partially returned to compressor 1 aftergoing through first solenoid valve 4, first capillary tube 5 and firstevaporator 6, thereby forming a first refrigerant circuit. In parallelto the foregoing first refrigerant circuit is formed a secondrefrigerant circuit starting from refrigerant branching unit 3, passingsecond solenoid 7, second capillary tube 8 and second evaporator 9, andreturning to compressor 1.

First evaporator 6 is installed in first cooling compartment 11 ofrefrigerator's main body 10 and second evaporator 9 is installed insecond cooling compartment 12. First controlling means 13 detects thetemperatures in first cooling compartment 11 and controlsclosing/opening of first solenoid 4. Second controlling means 14 detectsthe temperatures in second cooling compartment 12 and controlsclosing/opening of second solenoid 7.

Next, a description is given to how the refrigerating unit structured asabove operates.

A refrigerant is compressed by compressor 1 and condensed by dissipatingheat in condenser 2. After passing refrigerant branching unit 3, therefrigerant is depressurized in first capillary tube 5 and evaporated infirst evaporator 6 when first solenoid 4 is open, thereby providingcooling for first cooling compartment 11. First controlling means 13controls closing/opening of first solenoid 4, thereby controlling firstcooling compartment 11 to a predetermined temperature.

Similarly, the refrigerant branched at refrigerant branching unit 3 isdepressurized in second capillary tube 8 and evaporated in secondevaporator 9 when second solenoid 7 is open, thereby providing coolingfor second cooling compartment 12. Second controlling means 14 controlsclosing/opening of second solenoid 7, thereby controlling second coolingcompartment 12 to a predetermined temperature. When the respectivecooling compartments are not allowed to be controlled only byclosing/opening of the respective solenoids, the respective coolingcompartments are controlled by operating and stopping of compressor 1.

A prior art refrigerator is disclosed in the Japanese Patent ApplicationUnexamined Publication No. H8-210753 of 1996.

A description is given to the aforementioned prior art refrigerator withreference to drawings.

FIG. 10 is a longitudinal cross-sectional view for showing an outlinestructure of the prior art refrigerator. FIG. 11 is a block diagram of acooling system of the prior art refrigerator. FIG. 12 is a block diagramfor showing an operation control circuit of the prior art refrigerator.

In FIG. 10, refrigerator's main body 15 has freezer compartment 16 andcold storage compartment 17 that are separated from each other toprevent chilled air from mixing therebetween. First evaporator 18 isinstalled in freezer compartment 16 and second evaporator 19 isinstalled in cold storage compartment 17. First air blower 20 isdisposed right next to first evaporator 18 and second air blower 21 isdisposed right next to second evaporator 19. Compressor 22 is installedin the lower back part of refrigerator's main body 15.

In FIG. 11, compressor 22, condenser 23, capillary tube 24 acting as apressure reducer, first evaporator 18, refrigerant tube 25 and secondevaporator 19 are connected in succession, thereby establishing a closedcircuit. Refrigerant tube 25 connects between first evaporator 18 andsecond evaporator 19.

Subsequently, as FIG. 12 shows, freezer compartment temperatureadjusting unit 27 to set up the temperatures of freezer compartment 16,cold storage compartment temperature adjusting unit 28 to set thetemperatures of cold storage compartment 17, freezer compartmenttemperature detecting means 29 to detect the temperatures of freezercompartment 16 and cold storage compartment temperature detecting means30 to detect the temperatures of cold storage compartment 17 areconnected to the input terminal of controlling means 26 acting as acontroller. First relay 31 and second relay 32 are connected to theoutput terminal of controlling means 26.

First switch 34, which is turned on/off according to the behavior offirst relay 31, is connected to one of the terminals of power supply 33.Compressor 22 and second switch 35 are connected to the output terminalof first switch 34. Aforementioned first air blower 20 is connected tocontact a of second switch 35. Aforementioned second air blower 21 isconnected to contact b of second switch 35.

Next, a description is given to how the refrigerator structured as aboveoperates.

A refrigerant is compressed by compressor 22 and condensed bydissipating heat in condenser 23. The condensed refrigerant is reducedin pressure in capillary tube 24 and part of the refrigerant isevaporated in first evaporator 18 and the balance of the refrigerant isevaporated while passing through second evaporator 19. Thus, a heatexchange reaction takes place in the respective evaporators. Then, therefrigerant in a gaseous state is sucked into compressor 22. Such arefrigeration cycle as above is repeated as compressor 22 is broughtinto operation.

By the action of a mechanical draft of first air blower 20 and secondair blower 21, the air in freezer compartment 16 and cold storagecompartment 17 undergoes a heat exchange in first evaporator 18 andsecond evaporator 19.

At this time, when the temperature detected by freezer compartmenttemperature detecting means 29 is higher than the temperature set up byfreezer compartment temperature adjusting unit 27, controlling means 26brings first relay 31 into operation to turn on first switch 34, therebybringing compressor 22 into operation. Further, when the temperaturedetected by cold storage compartment temperature detecting means 30 ishigher than the temperature set up by cold storage compartmenttemperature adjuster 28, controlling means 26 connects second relay 32to contact b of second switch 35, thereby bringing second air blower 21into operation. As a result, cold storage compartment 17 undergoescooling selectively and is controlled to a predetermined temperature.

On the other hand, when the temperature detected by freezer compartmentdetecting means 29 is higher than the temperature set up by freezercompartment temperature adjusting unit 27 and the temperature detectedby cold storage compartment temperature detecting means 30 is lower thanthe temperature set up by cold storage compartment temperature adjustingunit 28, controlling means 26 connects second relay 32 to contact a ofsecond switch 35, thereby bringing first air blower 20 into operation.As a result, freezer compartment 16 undergoes cooling selectively and iscontrolled to a predetermined temperature.

When the temperature detected by freezer compartment temperaturedetecting means 29 is lower than the temperature set up by freezercompartment temperature adjusting unit 27, controlling means 26 bringsfirst relay 31 into operation to turn off first switch 34, therebybringing compressor 22 to a halt.

However, the structure of the prior art refrigerating unit is such thatcooling control of each respective cooling compartment is exercised byon/off of respective solenoids or operation/halt of respectivecompressors, thereby bringing about big fluctuations in temperature ofrespective evaporators and also cooling compartments. As a result, thereexists a drawback of the inability to maintain good quality of what isstored for a long period.

Since a capillary tube is used as a pressure reducing means for eachrespective evaporator, the evaporation temperature of each respectiveevaporator is determined by the entrance pressure of the evaporator.Therefore, the evaporator's evaporation temperature is not variable anduncontrollable. As result, the efficiency of a refrigerating unit is notenhanced sufficiently and there exists a drawback of not allowing theelectric power consumption to be reduced enough.

The present invention is to provide a high efficiency refrigerating unitby allowing the temperature variation of an object to be cooled causedby an evaporator to be minimized.

In the structure of the prior art refrigerator as described in above,first evaporator 18 and second evaporator 19 linked by refrigerant tube25 and, therefore, the evaporation temperatures of respectiveevaporators are almost the same. In addition, since cooling control offreezer compartment 16 and cold storage compartment 17 is exercised byoperation control of first air blower 20 and second air blower 21,electric power is consumed wastefully, in particular, due to a declinein cooling efficiency caused by cooling at an unnecessarily lowtemperature that takes place in cold storage compartment 17 where greattemperature differentials exist in comparison with the evaporationtemperature. Further, a compartment temperature variation and a humiditydecline occur, thereby bringing about such a drawback as degrading thequality of foods in storage due to temperature stresses imposed on thefoods or accelerated drying of the foods.

The present invention provides a refrigerator exhibiting a high coolingefficiency and achieving high storage quality of foods by bringing theevaporation temperature of each respective evaporator closer to thetemperature set up for each respective cooling compartment.

SUMMARY OF THE INVENTION

A refrigerating unit of the present invention comprises:

(a) a compressor;

(b) a condenser;

(c) a plurality of evaporators connected in series;

(d) a capillary tube disposed between the condenser and each of theplurality of evaporators;

(e) a refrigerant flow rate adjustable unit disposed between respectiveevaporators of the plurality of evaporators; and

(f) a refrigerant,

in which the compressor, condenser, evaporator, capillary tube,refrigerant flow rate adjustable unit and refrigerant constitute arefrigeration cycle,

the refrigerant is circulated in the refrigeration cycle, and

the refrigerant flow rate adjustable unit controls respectiveevaporation temperatures of the plurality of evaporators.

The refrigerant flow rate adjustable unit is preferred to control a flowof the refrigerant in such a way as the evaporation temperature of eachrespective evaporator located at the upstream side of the refrigerationcycle is made higher than the evaporation temperature of each respectiveevaporator located at the downstream side of the refrigeration cycle.

Preferably, the refrigerating unit further comprises:

(f) a bypass circuit to bypass at least one evaporator of the pluralityof evaporators,

in which the bypass circuit is disposed in parallel with the at leastone evaporator,

the compressor, condenser, evaporator, capillary tube, refrigerant flowrate adjustable unit, bypass circuit and refrigerant constitute arefrigeration cycle,

the refrigerant is circulated in the refrigeration cycle, and

the refrigerant flow rate adjustable unit controls respectiveevaporation temperatures of the plurality of evaporators variably.

A refrigerator of the present invention comprises a plurality of coolingcompartments and the refrigerating unit as described in above.

It is also preferred that each respective cooling compartment of theplurality of cooling compartments has a set up temperature that isdifferent from one another, the evaporators are disposed in a coolingcompartment of the plurality of cooling compartments, respectively, andthe respective evaporators located at the upstream side of therefrigeration cycle are, in succession, disposed in a coolingcompartment having a higher set up temperature.

Accordingly, each respective evaporator has a proper evaporationtemperature. Therefore, the refrigeration cycle efficiency is enhanced,resulting in a reduction of the amount of energy consumed. In additionto achieving the foregoing advantage, a refrigerator having enhancedstorage quality for the foods stored is made available.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigeration system diagram of a refrigerating unit inexemplary embodiment 1 of the present invention.

FIG. 2 is a Mollier chart of the refrigerating unit in exemplaryembodiment 1 of the present invention.

FIG. 3 is a refrigeration system diagram of a refrigerating unit inexemplary embodiment 2 of the present invention.

FIG. 4 is a Mollier chart of the refrigerating unit in exemplaryembodiment 2 of the present invention.

FIG. 5 is a refrigeration system diagram of a refrigerating unit inexemplary embodiment 3 of the present invention.

FIG. 6 is a Mollier chart of the refrigerating unit in exemplaryembodiment 3 of the present invention.

FIG. 7 is a cross-sectional view of a refrigerator, which is equippedwith a present invention's refrigerating unit, in exemplary embodiment 4of the present invention.

FIG. 8 is a block diagram of the operation control circuit of therefrigerator in exemplary embodiment 4 of the present invention.

FIG. 9 is a refrigeration system diagram of a prior art refrigeratingunit

FIG. 10 is a cross-sectional view of a prior art refrigerator.

FIG. 11 is a refrigeration system diagram of the prior art refrigerator.

FIG. 12 is a block diagram of the operation control circuit of the priorart refrigerator.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A refrigerating unit in an exemplary embodiment of the present inventioncomprises a compressor, a condenser, a plurality of evaporatorsconnected in series, a capillary tube disposed between the condenser andthe evaporator and a refrigerant flow rate adjustable unit disposedbetween evaporators of the plurality of evaporators, and the compressor,condenser, plurality of evaporators, capillary tube and the refrigerantflow rate adjustable unit constitute a refrigeration cycle, and alsorefrigerant flow rate adjustable unit controls the rate of refrigerantflow, thereby having respective evaporation temperatures of theplurality of evaporators set to a higher value in succession startingfrom the upstream side of the refrigeration cycle. Accordingly, bycombining the capillary tube and the throttling action of therefrigerant flow rate adjustable unit, the respective evaporationtemperatures of the plurality of evaporators are ratcheted down insuccession, resulting in a differentiation of the evaporationtemperatures. In addition, each respective evaporator is set to a properevaporation temperature, thereby enhancing the efficiency ofrefrigeration cycle.

A refrigerating unit in another exemplary embodiment of the presentinvention comprises a compressor, a condenser, a plurality ofevaporators connected in series, a capillary tube disposed between thecondenser and the evaporator, a refrigerant flow rate adjustable unitdisposed between evaporators of the plurality of evaporators and abypass circuit bypassing at least one evaporator of the plurality ofevaporators, and the compressor, condenser, plurality of evaporators,refrigerant flow rate adjustable unit, capillary tube and bypass circuitconstitute a refrigeration cycle, and also the refrigerant flow rateadjustable unit controls the evaporation temperatures of the pluralityof evaporators variably. Accordingly, a desired evaporation temperaturefor each respective evaporator is adjusted arbitrarily. As a result, acooling function exhibiting proper and high efficiency comes into play.Furthermore, when cooling of an evaporator of interest is not needed,that particular evaporator is bypassed, thereby allowing only theevaporators requiring cooling to be cooled down in a concentratedmanner. Therefore, wasteful cooling can be avoided.

A refrigerating unit in still another exemplary embodiment of thepresent invention comprises a compressor, a condenser, a firstevaporator and a second evaporator connected in series, a refrigerantflow rate adjustable unit disposed between the first evaporator and thesecond evaporator, a capillary tube disposed between the condenser andthe first evaporator, and a bypass circuit to bypass the firstevaporator and the refrigerant flow rate adjustable unit, and thecompressor, condenser, first evaporator, second evaporator, refrigerantflow rate adjustable unit, capillary tube and bypass circuit constitutea refrigeration cycle, and also the flow rate of refrigerant iscontrolled by the refrigerant flow rate adjustable unit, therebyallowing the evaporation temperature of the first evaporator to be setto a temperature higher than the evaporation temperature of the secondevaporator.

Accordingly, each respective evaporation temperature of the firstevaporator and the second evaporator is adjusted arbitrarily to realizea differentiation of the evaporation temperatures. When cooling of thefirst evaporator is not needed, the first evaporator is bypassed,thereby allowing the refrigerant to flow in the second evaporator in aconcentrated manner and eliminating the energy waste by performingcooling in the necessary evaporators only. In addition, the temperaturefluctuations due to excessive cooling of the object to be cooled by thefirst evaporator are suppressed.

It is preferred that the refrigerant flow rate adjustable unit has atotally closing function and the totally closing function is put intooperation when the evaporator disposed in parallel with the bypasscircuit is not required to be cooled. Accordingly, a highly accurateflow rate control is carried out less costly and also reliablerefrigerant flow channel switching is made possible.

Preferably, the aforementioned totally closing function is performedwhen the evaporator disposed in parallel with the bypass circuit isdefrosted under an off cycle state, thereby allowing the defrosting totake place without wasting electric power in defrosting heaters and thelike.

A refrigerator in an exemplary embodiment of the present inventioncomprises the refrigerating unit as described in above, a plurality ofcooling compartments for keeping foods cold and in storage and arefrigerating unit, and each evaporator of a plurality of evaporators isdisposed in the cooling compartment, respectively, each being set to ahigher temperature in succession starting from the upstream side of arefrigeration cycle. Accordingly, the respective evaporationtemperatures of the plurality of evaporators are controlled variably. Inaddition, by setting properly the evaporation temperature of eachrespective evaporator, the changes in temperature and dryness aresuppressed such that the difference between the storage temperature ofthe foods stored and the cold air temperature is reduced.

A refrigerator in another exemplary embodiment of the present inventioncomprises the refrigerating unit as described in above, a cold storagetemperature compartment, a freezer temperature compartment and arefrigerating unit, and a first evaporator is disposed in the coldstorage temperature compartment and a second evaporator is disposed inthe freezer temperature compartment. Accordingly, the temperaturedifference between the first evaporator and the second evaporator ismaintained sufficiently large. As a result, the temperature differencerequired of the cold storage compartment and the freezer compartment isrealized efficiently. In addition, the difference between the coldstorage compartment temperature that is above zero ° C. and theevaporation temperature of the first evaporator is reduced, therebyallowing the temperature changes and dehumidifying action of the coldstorage compartment to be suppressed.

Preferably, the extent of throttling of a refrigerant flow rateadjustable unit is controlled such that the temperature differencebetween the evaporation temperature of respective evaporators and thecompartment temperature is not exceeding 5° C., thereby furthersuppressing the temperature changes and dryness in the coolingcompartment and also enhancing the efficiency of refrigeration cycle.

Preferably, the evaporation temperature of the first evaporator iscontrolled to range from −5° C. to 5° C., thereby bringing about afurther reduction in the difference between the cold storage compartmentand the evaporation temperature of the first evaporator. As a result,the temperature changes and dehumidifying action of the cold storagecompartment are further suppressed.

Preferably, the refrigerant flow rate adjustable unit is installed inthe freezer temperature compartment, thereby reducing the frosting on anelectric expansion valve. As a result, the defrosting operation isfacilitated.

Preferably, when the freezer temperature compartment is rapidly cooleddown, the extent of throttling of the refrigerant flow rate adjustableunit is increased and the evaporation temperature of the secondevaporator is lowered. Accordingly, the temperature of the cold air fedto the freezer compartment is lowered, thereby accelerating therefrigeration speed of foods and the like and enhancing the effect ofrapid refrigeration.

Next, a description is given to a refrigerating unit and a refrigeratorequipped with the refrigerating unit in exemplary embodiments of thepresent invention with reference to drawings.

Exemplary Embodiment 1

FIG. 1 is a refrigeration system diagram of a refrigerator equipped witha refrigerating unit in exemplary embodiment 1 of the present invention.FIG. 2 is a Mollier chart of a refrigeration cycle of the refrigeratorequipped with the refrigerating unit of the present exemplaryembodiment.

In FIG. 1, refrigerator's main body 101 comprises cold storagecompartment 102 and freezer compartment 103, first evaporator 104 isdisposed in cold storage compartment 102 and second evaporator 105 isdisposed in freezer compartment 103. Refrigerant flow rate adjustableunit 106 comprising an electric expansion valve and the like is disposedbetween first evaporator 104 and second evaporator 105.

Compressor 107, condenser 108, capillary tube 109, first evaporator 104,compressor 107, suction pipe 110 and second evaporator 105 constitute aring-shaped refrigeration cycle. Suction pipe 110 connects betweensecond evaporator 105 and compressor 107. First evaporator 104 andsecond evaporator 105 are connected in series.

First air blower 111 causes a forced heat exchange to take place in theair between first evaporator 104 and cold storage compartment 102.Second air blower 112 causes a forced heat exchange to take place in theair between second evaporator 105 and freezer compartment 103. Firstevaporator temperature detecting means 113 is disposed near the outletof first evaporator 104. Cold storage compartment temperature detectingmeans 114 detects the temperatures in cold storage compartment 102.Second evaporator temperature detecting means 115 is disposed near theoutlet of second evaporator 105. Freezer compartment temperaturedetecting means 116 detects the temperatures in freezer compartment 103.

According to the information from first evaporator temperature detectingmeans 113, cold storage compartment temperature detecting means 114,second evaporator temperature detecting means 115 and freezercompartment temperature detecting means 116, controlling means 117controls the opening of refrigerant flow rate adjustable unit 106.

According to the setup as described in above, a refrigerant iscompressed by compressor 107 and the compressed refrigerant dissipatesheat and is condensed in condenser 108, and then enters in capillarytube 109. The refrigerant condensed and reduced in pressure enters infirst evaporator 104 and evaporates at the saturation temperature undera pressure corresponding to the extent of throttling (opening) ofrefrigerant flow rate adjustable unit 106.

When the opening of refrigerant flow rate adjustable unit 106 is large,the refrigerant pressure becomes close to the suction pressure (lowpressure) of compressor 107, resulting in a low evaporation temperatureon the part of first evaporator 104. Conversely, when the opening ofrefrigerant flow rate adjustable unit 106 is small, the pressure infirst evaporator 104 becomes high, resulting in a high evaporationtemperature. The evaporation temperatures of first evaporator 104 arecontrolled by adjusting the opening of refrigerant flow rate adjustableunit 106 via controlling means 117. Controlling means 117 goes intoaction based on the information from first evaporator temperaturedetecting means 113 and cold storage compartment temperature detectingmeans 114. Then, the refrigerant reduced in pressure by refrigerant flowrate adjustable unit 106 evaporates in second evaporator 105 and returnsto compressor 107 via suction pipe 110.

A description is given to the above operation with reference to theMollier chart of FIG. 2. The refrigerant is changed in state from pointA to point B by condenser 108 and reduced in pressure from point B topoint C by capillary tube 109 and then enters in first evaporator 104 atpoint C on the Mollier chart. The refrigerant that enters in firstevaporator 104 evaporates at the saturation temperature under pressureP1. Point D indicates the inlet to refrigerant flow rate adjustable unit106 and the refrigerant is reduced in pressure to point E correspondingto the outlet of refrigerant flow rate adjustable unit 106 in position,enters in second evaporator 105 and evaporates at the saturationtemperature under pressure P3. Then, the refrigerant is sucked incompressor 107 at point F and compressed to point A. When the opening ofrefrigerant flow rate adjustable unit 106 is narrowed down at thispoint, point C is shifted to point Cp and point D to point Dp, therebyincreasing the refrigerant pressure to P2 and moving upward theevaporation temperature of first evaporator 104. Conversely, when theopening of refrigerant flow rate adjustable unit 106 is expanded, thepressure of point C is declined and the evaporation temperature of firstevaporator 104 is also lowered.

Therefore, when cold storage compartment 102 is kept at a cold storagetemperature (0° C. to 5° C., for example,) by first evaporator 104 andfirst air blower 111, the opening of refrigerant flow rate adjustableunit 106 is controlled such that the difference in temperature betweenthe inside of cold storage compartment 102 and first evaporator 104 iskept small (around 5° C., for example). As a result, the temperaturechanges in cold storage compartment 102 become small.

When the difference in temperature between the inside of cold storagecompartment 102 and first evaporator 104 is small, the dehumidifyingaction in cold storage compartment 102 is allowed to be suppressed,thereby keeping the humidity in cold storage compartment 102 high andpreventing the foods stored therein from becoming dry.

By controlling the opening of refrigerant flow rate adjustable unit 106periodically (once an hour or so, for example) such that the evaporationtemperature of first evaporator 104 is kept at around 5° C. to 10° C.,first evaporator 104 is allowed to be defrosted without needing aspecial heating unit, thereby preventing the increase in temperature ofcold storage compartment 102. As a result, savings in production costsinvolved with the heating unit are achieved.

In addition, since the difference between the temperature of coldstorage compartment 102 and the evaporation temperature of firstevaporator 104 becomes small, thereby allowing the evaporationtemperature to be set somewhat high, the efficiency of refrigerationcycle is enhanced and greater energy savings are made possible.

When the load imposed on cold storage compartment 102 is heavy or duringthe initial period of installing a refrigerator for use, the amount ofrefrigerant in circulation is increased by controlling the opening ofrefrigerant flow rate adjustable unit 106, thereby allowing the periodof time needed for cooling down to a predetermined temperature to beshortened.

Further, by controlling the opening of refrigerant flow rate adjustableunit 106, it becomes possible for cold storage compartment 102 to havethe capabilities of acting as a temperature selector whereby anytemperatures ranging from a cold storage compartment temperature to afreezer compartment temperature are freely selected. Thus, arefrigerator having the great convenience to customers and satisfyingthe customers' requirements is made available.

On the other hand, freezer compartment 103 is kept at a predeterminedtemperature (a freezer compartment temperature of −20° C., for example)by second evaporator 105 and second air blower 112. And, when the loadimposed on freezer compartment 103 becomes heavy, the opening ofrefrigerant flow rate adjustable unit 106 is controlled according to theinformation from first evaporator temperature detecting means 113, coldstorage compartment temperature detecting means 114, second evaporatortemperature detecting means 115 and freezer compartment temperaturedetecting means 116, thereby increasing the amount of refrigerant incirculation of freezer compartment 103. As a result, the temperature offreezer compartment 103 is adjusted to a predetermined temperature in ashort period of time. Conversely, when the load imposed on cold storagecompartment 102 and freezer compartment 103 is light, the opening ofrefrigerant flow rate adjustable unit 106 is controlled such that theamount of refrigerant in circulation is reduced, thereby enhancing thesystem efficiency and achieving energy savings.

Controlling means 117 evaluates the information from first evaporatortemperature detecting means 113 and cold storage temperature detectingmeans 114. As a result of the evaluation, the opening of refrigerantflow rate adjustable unit 106 is controlled such that the evaporationtemperature of first evaporator 104 for cold storage compartment 102 isadjusted to range from −5° C. to 5° C. Furthermore, the efficiency ofrefrigeration cycle is enhanced and the difference between theevaporation temperature of first evaporator 104 and the temperature ofcold storage compartment 102 is further reduced, thereby enabling thetemperature changes of cold storage compartment 102 to be furtherreduced. A higher evaporation temperature of first evaporator 104 allowsthe dehumidifying action against cold storage compartment 102 to besuppressed, thereby enhancing the storage quality further by keepingcold storage compartment 102 at a high humidity and preventing the foodsstored from becoming dry.

Furthermore, when freezer compartment 103 is required to have the foodsfrozen rapidly for the purpose of home freezing of foods, controllingmeans 117 evaluates the information from first evaporator temperaturedetecting means 113, cold storage temperature detecting means 114,second evaporator temperature detecting means 115 and freezercompartment temperature detecting means 116. As a result of theevaluation, the opening of refrigerant flow rate adjustable unit 106 isreduced in extent such that the evaporation temperature of secondevaporator 105 is lowered, thereby making the cold air supplied tofreezer compartment 103 by second air blower 112 lower in temperatureand enabling the foods stored to be frozen rapidly.

Although first evaporator 104 is disposed in cold storage compartment102 in the present exemplary embodiment, the location of firstevaporator 104 is not restricted to above and can be anywhere in thevicinity of the cold storage temperature zone. And, first evaporator 104is disposed near the temperature zone requiring the control oftemperatures apart from the freezer compartment temperature zone andcomprising the temperatures of a vegetable compartment at a cold storagetemperature, a low temperature compartment belonging to the range of lowtemperature storage (encompassing such compartments with a temperaturezone of around −5° C. to 0° C. as a partial freezing compartment, icecold compartment, chilled foods compartment, etc.) and the like.

Exemplary Embodiment 2

FIG. 3 is a refrigeration system diagram of a refrigerator equipped witha refrigerating unit in exemplary embodiment 2 of the present invention.FIG. 4 is a Mollier chart of a refrigeration cycle of the refrigeratorequipped with a refrigerating unit of the present exemplary embodiment.

In FIG. 3, compressor 201, condenser 202, first evaporator 203, secondevaporator 204 and third evaporator 205 are connected in series.Capillary tube 206 is connected between the outlet of condenser 202 andthe inlet of first evaporator 203. Refrigerant flow rate adjustable unit207 is disposed between first evaporator 203 and second evaporator 204.Refrigerant flow rate adjustable unit 208 is disposed between secondevaporator 204 and third evaporator 205. As refrigerant flow rateadjustable units 207 and 208 are used an electric expansion valve andthe like, for example. Suction pipe 209 connects between the out let ofthird evaporator 205 and compressor 201. Thus, a ring-shapedrefrigeration cycle is formed.

First evaporator 203 is disposed in first cooling compartment 211 wheretemperatures are set to the highest value in refrigerator's main body210. Second evaporator 204 is disposed in second cooling compartment 212where temperatures are set to the second-highest value in refrigerator'smain body 210. Third evaporator 205 is disposed in third coolingcompartment 213 where temperatures are set to the lowest value.

First air blower 214 is installed in first cooling compartment 211.Second air blower 215 is installed in second cooling compartment 212.Third air blower 216 is installed in third cooling compartment 213.First evaporator temperature detecting means 217 is located near theoutlet of first evaporator 203. First cooling compartment temperaturedetecting means 218 detects the temperatures in first coolingcompartment 211. Second evaporator temperature detecting means 219 islocated near the outlet of second evaporator 203. Second coolingcompartment temperature detecting means 220 detects the temperatures insecond cooling compartment 212. Third evaporator temperature detectingmeans 221 is located near the outlet of third evaporator 205. Thirdcooling compartment temperature detecting means 222 detects thetemperatures in third cooling compartment 213.

Based on the information from first evaporator temperature detectingmeans 217, first cooling compartment temperature detecting means 218,second evaporator temperature detecting means 219, second coolingcompartment temperature detecting means 220, third evaporatortemperature detecting means 221 and third cooling compartmenttemperature detecting means 222, controlling means 223 adjusts theopening of refrigerant flow rate adjustable units 207 and 208,respectively.

Next, a description is given to how the refrigeration cycle constitutedas above behaves.

The refrigerant compressed in compressor 201 dissipates heat and iscondensed in condenser 202, and then enters in capillary tube 206. Thede-pressurized liquid refrigerant enters in first evaporator 203 andsecond evaporator 204 and then part of the liquid refrigerant evaporatesat the saturation temperature under a pressure corresponding to theextent of throttling (opening) of refrigerant flow rate adjustable units207 and 208, respectively. When the opening of refrigerant flow rateadjustable unit 207 is increased, the evaporation temperature of firstevaporator 203 is lowered since the evaporation pressure of firstevaporator 203 becomes closer to that of second evaporator 204.Conversely, when the opening of refrigerant flow rate adjustable unit 20is reduced, the pressure in first evaporator 203 is increased, therebyleading to a higher evaporation temperature.

Controlling of the evaporation temperatures of first evaporator 203 andsecond evaporator 204 is performed by adjusting the opening ofrefrigerant flow rate adjustable units 207 and 208 via controlling means223, respectively. The information of evaporation temperaturecontrolling is furnished by first evaporator temperature detecting means217, first cooling compartment temperature detecting means 218, secondevaporator temperature detecting means 219, second cooling compartmenttemperature detecting means 220, third evaporator temperature detectingmeans 221 and third cooling compartment temperature detecting means 222.

And, the refrigerant that remains after depressurization performedfurther in refrigerant flow rate adjustable units 207 and 208 evaporatesin third evaporator 205 at the evaporation temperature corresponding toa suction pressure (low pressure) of compressor 201 and returns tocompressor 201 via suction pipe 209.

A description is given to the above operation with reference to theMollier chart of FIG. 4. The refrigerant is changed in state from pointA1 to point B1 by condenser 202 and reduced in pressure from point B1 topoint C1 by capillary tube 206. The refrigerant that enters in firstevaporator 203 at point C1 on the Mollier chart evaporates at thesaturation temperature under pressure Pa. Point D1 indicates the inletto refrigerant flow rate adjustable unit 207, and the refrigerant isreduced in pressure to point E1 corresponding to the outlet ofrefrigerant flow rate adjustable unit 207 in position, enters in secondevaporator 204 and evaporates at the saturation temperature underpressure Pb. Point F1 is the inlet of refrigerant flow rate adjustableunit 208, and the refrigerant is reduced in pressure to point G1corresponding to the outlet of refrigerant flow rate adjustable unit 208in position, enters in third evaporator 205 and evaporates at thesaturation temperature under pressure Pc. Then, the refrigerant issucked in compressor 201 at point H1 and compressed to point A1.

When the opening of refrigerant flow rate adjustable unit 207 isnarrowed down at this point, point C1 is shifted to point C1 p and pointD1 to point D1 p, thereby increasing the pressure of the refrigerant toPd and moving upward the evaporation temperature of first evaporator203. Conversely, when the opening of refrigerant flow rate adjustableunit 207 is expanded, the pressure of point C1 is declined and theevaporation temperature of first evaporator 203 is lowered.

Therefore, when the temperature of first cooling compartment 211 havingthe highest value as the set up temperature is kept at a cold storagetemperature (0° C. to 5° C., for example), the opening of refrigerantflow rate adjustable unit 207 is adjusted to increase the evaporationtemperature of first evaporator 203, resulting in a reduction of thedifference in temperature between the cooling compartment and theevaporator. As a result, the temperature of cold air sent in by firstair blower 215 is prevented from being lowered excessively, therebyreducing the temperature changes in the cooling compartment andsuppressing the dehumidifying action. Therefore, the storage quality offoods stored in first cooling compartment 211 is enhanced. Also, theevaporation temperatures are increased appropriately and the efficiencyof refrigeration cycle is enhance, resulting in achieving energysavings.

By controlling the opening of refrigerant flow rate adjustable units 207and 208 periodically (once an hour or so, for example) such that theevaporation temperatures of first evaporator 203 and second evaporator204 are kept at around 5° C. to 10° C., respectively, there is no needof a special heating unit to defrost the evaporators, thereby preventingthe increase in temperature of the cooling compartment. As a result,savings in production costs involved with the heating unit are achieved.

When the load imposed on the cooling compartment is heavy or during theinitial period of installing a refrigerator for use, the amount ofrefrigerant in circulation is increased by controlling the respectiveopenings of refrigerant flow rate adjustable units 207 and 208, therebyallowing the period of time needed for adjusting to a predeterminedtemperature to be shortened.

Also, third cooling compartment 213 is kept at a predeterminedtemperature (a freezer temperature of −20° C., for example) by thirdevaporator 205 and third air blower 217. When the load imposed on thecooling compartment becomes heavy, the respective openings ofrefrigerant flow rate adjustable units 207 and 208 are adjusted based onthe information from first evaporator temperature detecting means 217,first cooling compartment temperature detecting means 218, secondevaporator temperature detecting means 219, second cooling compartmenttemperature detecting means 220, third evaporator temperature detectingmeans 221 and third cooling compartment temperature detecting means 222,thereby increasing the amount of refrigerant in circulation and allowingthe temperature of the cooling compartment to be adjusted to apredetermined temperature in a short period of time. Conversely, whenthe load imposed on the cooling compartment is light, the respectiveopenings of refrigerant flow rate adjustable units 207 and 208 arecontrolled such that the amount of refrigerant in circulation isreduced, thereby enhancing the system efficiency and achieving energysavings.

Further, by controlling the respective openings of refrigerant flow rateadjustable units 207 and 208, it becomes possible for the temperaturesof first cooling compartment 211 and second cooling compartment 212 tobe set to a temperature ranging from a cold storage temperature to afreezing temperature freely. Thus, a refrigerator having the greatconvenience to customers and satisfying the customers' requirements ismade available.

The information from first evaporator temperature detecting means 217,first cooling compartment temperature detecting means 218, secondevaporator temperature detecting means 219, second cooling compartmenttemperature detecting means 220, third evaporator temperature detectingmeans 221 and third cooling compartment temperature detecting means 222is evaluated by controlling means 223. Based on the information, therespective openings of refrigerant flow rate adjustment units 207 and208 are adjusted such that the difference between the evaporationtemperature of an evaporator in each respective cooling compartment andthe temperature inside of each respective cooling compartment does notexceed 5° C., thereby allowing the temperature changes and dehumidifyingaction in each respective cooling compartment to be suppressed. Theproper evaporation temperatures and the proper amount of refrigerant incirculation allow further enhancement of system efficiency and savingsof energy to be realized.

Although the present exemplary embodiment deals with a refrigeratorcomprising three cooling compartments and evaporators, the presentinvention is not restricted to above by any means and the followingconfigurations are also possible. For example, each respective coolingcompartment of the three cooling compartments is assigned with thefunction of serving as a cold storage compartment, a low temperaturecompartment or a freezer compartment by setting the evaporationtemperature of each of the foregoing compartments to the intendedtemperature zone with a successive reduction of evaporation temperature.Thus, a cooling function separate from one another is provided to eachrespective cooling compartment. As a result, the optimum efficiency inrefrigeration cycle is realized and also the most suitable storagequality for foods stored is achieved.

Exemplary Embodiment 3

FIG. 5 is a refrigeration system diagram of a refrigerating unit inexemplary embodiment 3 of the present invention. FIG. 6 is a Mollierchart of the refrigerating unit in exemplary embodiment 3 of the presentinvention. In FIG. 5, the refrigerating unit comprises compressor 301,condenser 302, first capillary tube 303, first evaporator 304 and secondevaporator 305. As refrigerant flow rate adjustable unit 306 is used anelectric expansion valve, for example, and the electric expansion valvehas a totally closing function. First capillary tube 303 connectsbetween the outlet of condenser 302 and the inlet of first evaporator304. Refrigerant flow rate adjustable unit 306 is disposed between firstevaporator 304 and second evaporator 305. Bypass circuit 307 isconnected to branch connection unit 308 disposed at the inlet of firstevaporator 304 and also to merging connection unit 309 disposed aat theoutlet of refrigerant flow rate adjustable unit 306. Bypass circuit 307is formed so as to bypass first evaporator 304. Second capillary tube310 having a relatively small amount of pressure reduction is providedin bypass circuit 307. Suction pipe 311 connects between the outlet ofsecond evaporator 305 and compressor 301. Thus, a refrigeration cycle isestablished.

Refrigerator's main body 312 has cold storage compartment 313 andfreezer compartment 314. First evaporator 304 is installed in coldstorage compartment 313 and second evaporator 305 is installed infreezer compartment 314. First air blower 315 is disposed in coldstorage compartment 313 and second air blower 316 is disposed in freezercompartment 314.

First evaporator temperature detecting means 317 is located near theinlet of first evaporator 304. Cold storage compartment temperaturedetecting means 318 detects the temperatures in cold storage compartment313. Second evaporator temperature detecting means 319 is located nearthe inlet of second evaporator 305. Freezer compartment temperaturedetecting means 320 detects the temperatures in freezer compartment 314.Controlling means 321 controls the opening of refrigerant flow rateadjustable unit 306 based on the information from first evaporatortemperature detecting means 317, cold storage compartment temperaturedetecting means 318, second evaporator temperature detecting means 319and freezer compartment temperature detecting means 320.

Next, a description is given to how the refrigerating unit structured asabove performs.

The refrigerant compressed in compressor 301 dissipates heat incondenser 302, is condensed and enters in first capillary tube 303. Thecondensed refrigerant that is reduced in pressure enters in firstevaporator 304 via branch connecting unit 308 and evaporates at thesaturation temperature of a pressure corresponding to the extent ofthrottling (opening) of refrigerant flow rate adjustable unit 306. Whenthe opening of refrigerant flow rate adjustable unit 306 is increased,the evaporation temperature of first evaporator 304 is lowered since therefrigerant pressure becomes closer to the suction pressure (lowpressure) of compressor 301. Conversely, when the opening is decreased,the pressure in evaporator 304 is increased and the evaporationtemperature is also increased.

In order to control the evaporation temperature of first evaporator 304,the opening of refrigerant flow rate adjustable unit 306 is adjusted bycontrolling means 321. The information needed for the foregoingcontrolling is furnished by first evaporator temperature detecting means317 and cold storage compartment temperature detecting means 318. Therefrigerant reduced further in pressure by refrigerant flow rateadjustable unit 306 is merged at merging connection unit 309 with partof the refrigerant flown into bypass circuit 307 at branch connectionunit 308 and flows into second evaporator 305. The refrigerant vaporizedin second evaporator 305 returns to compressor 301 via suction pipe 311.

At this time, the electric expansion valve serving as refrigerant flowrate adjustable unit 306 has a totally closing function. When cooling infirst evaporator 304 is judged as no longer needed (a judgement madethrough the temperature detected by cold storage compartment temperaturedetecting means 318, for example) or the frost formed on firstevaporator 304 is defrosted under an off cycle state (a periodicaloperation performed one time or so for every 2 to 3 hours, for example),the totally closing function of the electric expansion valve is carriedout. When the electric expansion valve is totally closed, therefrigerant flows into bypass circuit 307 at branch connection unit 308at the time when compressor 301 is in operation and then flows in secondevaporator 305 via merging connection unit 309. The refrigerantevaporates in second evaporator 305 and the evaporated refrigerantreturns to compressor 301 via suction pipe 311.

A description is given to the above operation with reference to theMollier chart of FIG. 6. Compressor 302 has the state of the refrigerantshifted from point A2 to point B2 and first capillary tube 303 has thepressure of the refrigerant reduced from point B2 to point C2. Therefrigerant having entered in first evaporator 304 at point C2evaporates at the saturation temperature against pressure Pe. Point D2corresponds to the inlet of refrigerant flow rate adjustable unit 306 inposition, and the refrigerant is reduced in pressure to point E2corresponding to the pressure at the outlet thereof, enters in secondevaporator 305 and evaporates at the saturation temperature againstpressure Pg.

And, the refrigerant is sucked into compressor 301 at point H2 andcompressed to point A2 on the Mollier chart.

When the opening of refrigerant flow rate adjustable unit 306 is madesmaller, point C2 is shifted to point C2 p and point D2 to point D2 p,and the refrigerant is increased in pressure to reach Pf, therebycausing the evaporation temperature of first evaporator 304 to increase.Conversely, when the opening of refrigerant flow rate adjustable unit306 is made larger, the pressure at point C2 is lowered, thereby causingthe evaporation temperature of first evaporator 304 also to be lowered.When the opening of refrigerant flow rate adjustable unit 306 is totallyclosed, the refrigerant flow into first evaporator 304 is suspended andthe refrigerant is further reduced in pressure in second capillary tube310 and enters in second evaporator 305 at point C2 h, where therefrigerant evaporates at the saturation temperature against pressurePh. And, the refrigerant is sucked into compressor 301 at point F2 andcompressed to reach point A2.

When cold storage compartment 313 is kept at a cold storage temperatures(1° C. to 5° C., for example) by first evaporator 304 and first airblower 315, the opening of refrigerant flow rate adjustable unit 306 isadjusted to make the evaporation temperature of first evaporator 304higher. The difference in temperature between the inside of cold storagecompartment 313 and the evaporation temperature of first evaporator 304is made smaller (around 3° C. to 5° C., for example) and kept constant,thereby allowing the excessive refrigeration of cold storage compartment313 due to cold air sent therein by first air blower 315 to be preventedfrom occurring during the cooling period of cold storage compartment313. As a result, the temperature changes in cold storage compartment313 are reduced.

Furthermore, when the difference in temperature between the inside ofcold storage compartment 313 and the evaporation temperature of firstevaporator 304 is made smaller, the dehumidifying action in cold storagecompartment 313 is suppressed. As a result, the inside of cold storagecompartment 313 is kept at a high humidity and the foods stored areprevented from becoming dry.

Therefore, the foods stored in cold storage compartment 313 are allowedto suppress the deterioration in quality caused by temperature changes(heat shock) applied to the foods. On top of that, drying of the foodsin storage is prevented, thereby enabling the enhancement of storagequality for the foods stored.

In addition, when the frost formed on first evaporator 304 isperiodically defrosted under an off cycle state once every 2 to 3 hours,for example, the electric expansion valve serving as refrigerant flowrate adjustable unit 306 is totally closed and also first blower 315 isoperated, thereby allowing the inside of cold storage compartment 313 tobe cooled down and also to be kept at a high humidity due to the coolingeffect caused by the heat of melting of frost and the humidifying actionof defrosted water.

Exemplary Embodiment 4

FIG. 7 is a cross-sectional view of a refrigerator in exemplaryembodiment 4 of the present invention. FIG. 8 is a block diagram forshowing an operation control circuit of the refrigerator of FIG. 7. InFIG. 7 and FIG. 8, refrigerator's main body 401 comprises at least oneof cold storage compartment 402 located in the upper part thereof, atleast one of freezer compartment 403 located in the lower part thereof,thermal insulation wall 404 and thermal insulation door 405.

A refrigeration cycle includes compressor 406, condenser 407, firstcapillary tube 408, cold storage compartment evaporator 409, electricexpansion valve 410 acting as a refrigerant flow rate adjustable unitand freezer compartment evaporator 411, all of which are connected inseries successively. In addition, branch connection unit 412 is disposedbetween first capillary tube 408 and cold storage compartment evaporator409 and merging connection unit 413 is disposed between electricexpansion valve 410 and freezer compartment evaporator 411. Secondcapillary tube 414 is disposed in bypass circuit 415. Electric expansionvalve 410 has a totally closing function.

Connection piping 416 connects between cold storage compartmentevaporator 409 and electric expansion valve 410 and also connectsbetween electric expansion valve 410 and freezer compartment 411. Thediameter of connection piping 416 is made large enough not to create alarge resistance against the passage of refrigerant. As a matter offact, connection piping 416 has almost the same diameter as the pipediameter of an evaporator.

Cold storage compartment evaporator 409 is located, for example, on thefurthermost surface in cold storage compartment 402. Near cold storagecompartment evaporator 409 are located cold storage compartment airblower 417 and cold storage duct 418 for moving the air inside of coldstorage compartment 402 to pass through cold storage compartmentevaporator 409 and to circulate around there.

Freezer compartment evaporator 411 is located, for example, on thefurthermost surface in freezer compartment 403. Near freezer compartmentevaporator 411 are located freezer compartment air blower 419 andfreezer duct 420 for moving the air inside of freezer compartment 403 topass through freezer compartment evaporator 411 and to circulate aroundthere.

Electric expansion valve 410 is disposed inside freezer compartment 403and adjusts the flow of refrigerant from cold storage compartmentevaporator 409 to freezer compartment evaporator 411 by controlling thevalve opening.

Merging connection unit 413 is also disposed inside freezer compartment403 near electric expansion valve 410, for example. The other connectionunit of branch connection unit 412 is located inside cold storagecompartment 403 near cold storage compartment evaporator 409, forexample.

Near freezer compartment evaporator 411 is disposed defrosting heater421.

Compressor 406 and condenser 407 are installed in machine compartment422 located in the furthermost corner of the lower part ofrefrigerator's main body 401.

Cold storage compartment temperature detecting means 423 is disposed incold storage compartment 402 and freezer compartment temperaturedetecting means 424 is disposed in freezer compartment 403. Cold storagecompartment evaporator temperature detecting means 425 is located nearcold storage compartment evaporator 409 and freezer compartmentevaporator temperature detecting means 426 is located near freezercompartment evaporator 411. Based on the information from respectivetemperature detecting means, controlling means 427 controls compressor406, electric expansion valve 410, cold storage compartment air blower417, freezer compartment air blower 419 and defrosting heater 421.

When defrosting heater 421 is turned on at regular intervals for thepurpose of defrosting freezer compartment evaporator 411, electricexpansion valve 410 is controlled by controlling means 427 to be put atfull opening.

Next, a description is given to how the refrigerator structured as inabove operates.

When freezer compartment 403 rises in temperature excessively, freezercompartment temperature detecting means 424 detects the fact that thetemperature of freezer compartment 403 has exceeded a predeterminedtemperature. Controlling means 427 receives a signal on the temperatureof freezer compartment 403 and puts compressor 406, freezer compartmentair blower 419 and electric expansion valve 410 into operation. The hightemperature and high pressure refrigerant discharged upon puttingcompressor 406 into operation is compressed and condensed in condenser407, reduced in pressure in first capillary tube 408 and reaches branchconnection unit 412.

When cold storage compartment temperature detecting means 423 detectsthe fact that the temperature of cold storage compartment 402 exceeds apredetermined temperature, electric expansion valve 410 takes the actionof opening the valve, thereby allowing the refrigerant to reach coldstorage compartment evaporator 409. Cold storage compartment air blower417 is put into operation and the air inside cold storage compartment402 is sucked in cold storage compartment evaporator 409 where a heatexchange takes place actively, thereby allowing the sucked air to bedischarged with the temperature thereof further lowered.

At this time, the opening of electric expansion valve 410 is adjustedsuch that the difference between the temperature set up for cold storagecompartment 402 and the temperature detected by cold storage compartmentevaporator temperature detecting means 425 is kept constant (5° C., forexample). As the temperature of the air inside cold storage compartment402 declines and when the temperature detected by cold storagecompartment temperature detecting means 423 is found to be lower than apredetermined temperature, controlling means 427 takes an action oftotally closing electric expansion valve 410. When the temperaturedetected by cold storage compartment temperature detecting means 423exceeds a predetermined temperature, cold storage compartment air blower417 is similarly put into operation. Conversely, when the detectedtemperature is found to be lower than the predetermined temperature,cold storage compartment air blower 417 ceases operation.

When electric expansion valve 410 is closed, the refrigerant flows inbypass circuit 415 formed of second capillary tube 414 via branchconnection unit 412 and then reaches freezer compartment evaporator 411after further reduced in pressure. By the operation of freezercompartment air blower 419, the air inside freezer compartment 403 issucked via freezer duct 420 in freezer compartment evaporator 411 wherea heat exchange takes place actively, thereby causing the refrigerant tobe vaporized. The vaporized refrigerant is again sucked in compressor406. The air having undergone a heat exchange is discharged with thetemperature thereof further lowered. As the temperature of the airinside freezer compartment 403 is lowered and when the temperaturedetected by freezer compartment temperature detecting means 424 is foundto be lower than a predetermined temperature, controlling means 427suspends the operation of compressor 406 and freezer compartment airblower 419, and electric expansion valve 410 is put into operation andclosed.

When electric expansion valve 410 is closed after the temperaturedetected by cold storage compartment temperature detecting means 423 ofcold storage compartment 402 is found to be exceeding a predeterminedtemperature, the refrigerant reaches cold storage compartment evaporator411 via branch connection unit 412 and then enters in freezercompartment evaporator 411 via electric expansion valve 410. Also, partof the refrigerant enters at branch connection unit 412 into secondcapillary tube 414, merges with the aforementioned refrigerant flow atmerging connection unit 413 and enters in freezer compartment evaporator411. The refrigerant evaporated in cold storage compartment evaporator409 and freezer compartment evaporator 411 is again sucked in compressor406.

At this time, when the difference between the temperature of coldstorage compartment 402 and the predetermined temperature is large, theopening of electric expansion valve 410 is increased, thereby enhancingthe cooling ability of cold storage compartment evaporator 409. When thedifference between the temperature of cold storage compartment 402 andthe predetermined temperature is small, the opening of electricexpansion valve 410 is decreased, thereby reducing the flow rate ofrefrigerant in cold storage compartment evaporator 409 and lowering thecooling ability of cold storage compartment evaporator 409. And, byputting cold storage compartment air blower 417 into operation, the airinside cold storage compartment 402 is sucked in via cold storage duct418 and a heat exchange takes place actively, thereby causing part ofthe refrigerant to be evaporated in cold storage compartment evaporator409. The air after the heat exchange is discharged and, when thetemperature of the discharged air is found lower than a predeterminedtemperature by the temperature detecting means, controlling means 427brings the operation of cold storage compartment air blower 417 tosuspension, and electric expansion valve 410 is closed by the totallyclosing action thereof.

Similarly, freezer compartment 403 is cooled down by putting freezercompartment air blower 419 into operation and, when the temperature offreezer compartment 403 is found lower than a predetermined temperatureby freezer compartment temperature detecting means 424, controllingmeans 427 brings the operation of compressor 406 and freezer compartmentair blower 419 to suspension, and electric expansion valve 410 is closedby the totally closing action thereof.

By repeating the operation as described in above, the refrigeratorundergoes cooling, and cold storage compartment 402 and freezercompartment 403 are cooled down to reach a predetermined temperature,respectively. When the evaporation temperature of cold storagecompartment evaporator 409 is maintained at −5° C., for example, bycontrolling the opening of electric expansion valve 410, the differencebetween the temperature of cold storage compartment 402 and theevaporation temperature is kept relatively small, thereby allowing thedehumidifying action to be suppressed and allowing the humidity insidecold storage compartment 402 to be kept high. As a result, the storagequality of foods is maintained at a high level.

As refrigerant flow rate adjustable unit 410 is used an electricexpansion valve which has the function of totally closing, therebyallowing the flow rate control to be performed less costly and yet witha high degree of accuracy. In addition, an accurate change-over actionbetween refrigerant flow channels is made possible. Therefore, whencooling of cold storage compartment evaporator 409 is no longer requiredbecause of the low ambient temperature or a small number of the objectsto be cooled, the refrigerant is directed to take a bypassing route inbypass circuit 415, thereby allowing the temperature changes of theobject to be cooled to be suppressed and allowing a high efficiencycooling action to be performed at an evaporation temperature that isappropriate to the object to be cooled. As a result, achievement ofenergy savings is made possible while excellent cooling performancebeing maintained.

Through the action of controlling means 427, cold storage compartmentair blower 417 is put into operation while electric expansion valve 410repeating the totally closing action (approximately once every 2 to 3hours, for example), thereby cooling down cold storage compartment 402while the frost formed on cold storage compartment evaporator 409 beingremoved by melting As a result, the humidifying action caused by thewater produced by defrosting brings the humidity inside cold storagecompartment 402 to a high level. Therefore, the periodical defrostingaction usually performed by means of a heater and the like becomes nolonger necessary.

Since electric expansion valve 410 is disposed inside freezercompartment 403, the humidity in freezer compartment 403 is low incomparison with cold storage compartment 402. Therefore, the forming offrost on electric expansion valve 410 is suppressed, thereby allowingthe frost formed on electric expansion valve 410 to be removed withreliability at the time of defrosting. As a result, the operation ofelectric expansion valve 410 is carried out properly and the respectivetemperatures of cold storage compartment 402 and freezer compartment 403are stabilized and kept at a predetermined temperature, respectively.

Since electric expansion valve 410 is disposed inside freezercompartment 403, the water content in cold storage compartment 402 isprevented from getting removed in the form of frost, thereby allowingthe interior of cold storage compartment 402 to be kept high in humidityand also allowing the foods in storage to be prevented from becomingdry.

For the purpose of defrosting freezer compartment evaporator 411,electric expansion valve 410 is totally opened when defrost heater 421is turned on periodically, thereby allowing the heat from defrost heater421 to be transferred to cold storage compartment evaporator 409 viarefrigerant. As a result, the defrosting of cold storage compartment 409is also carried out without fail.

Accordingly, the refrigerator of the present exemplary embodimentenables the quality degradation of foods stored in cold storagecompartment 402 due to a temperature variation (heat shock) to bereduced and also enables the foods in storage to be prevented frombecoming dry. As a result, the storage quality of foods is enhanced.

Furthermore, the extent of cooling for cold storage compartmentevaporator 409 installed in parallel to bypass circuit 415 is properlyadjusted and defrosting under an off cycle state is made possible.

Also, frosting on electric expansion valve 410 is prevented, therebyenhancing the reliability of the refrigerator.

Although the plurality of cooling compartments include cold storagecompartment 402 and freezer compartment 403 and an evaporator of arelatively high evaporation temperature zone is installed in coldstorage compartment 402 according to the present exemplary embodiment,the architecture of a refrigerator is not limited to above. Instead,such an architecture as the plurality of cooling compartments beinginclusive of a vegetable compartment and a bottled drink compartment,and an evaporator being disposed in the respective compartments ordisposed commonly in these compartments can be employed with the sameadvantages as the foregoing made attainable.

Industrial Applicability

According to the structure as described in above, a capillary tube andthe throttling action of a refrigerant flow rate adjustable unittogether realize a differentiation in evaporation temperatures in astable manner for a plurality of evaporators even with a refrigerationcycle characterized by a relatively small amount of refrigerant incirculation. As a result, the efficiency of refrigeration cycle isenhanced at a properly established evaporation temperature for eachrespective evaporator, thereby enabling the realization of energysavings.

The cooling function exhibiting a high efficiency at a desiredevaporation temperature for each respective evaporator is allowed tocome into play. When cooling of an evaporator of interest is not needed,the evaporator is bypassed, thereby enabling the cooling to be focusedonly on the evaporators needed to be cooled down, thereby avoidingwasteful cooling and realizing savings in electric power.

Efficient cooling at each respective evaporation temperature is madepossible. When a first evaporator is not needed to be cooled down, thefirst evaporator is bypassed and the refrigerant is circulated in asecond evaporator only, thus allowing the loss in cooling to beprevented from occurring.

A high-precision and less costly refrigerant flow rate control and areliable refrigerant flow channel switching action are made possible,thereby realizing the enhancement of refrigeration cycle efficiency.

The electric power consumed in defrosting by a defrost heater and thelike can be cut back.

The evaporation temperatures of a plurality of evaporators areadjustable/controllable, resulting in a reduction of the differencebetween the storage temperature of foods in storage and the cooled airtemperature at the proper evaporation temperature of each respectiveevaporator. Therefore, temperature changes and also drying of foods canbe prevented from occurring.

Existence of a difference in evaporation temperature between a firstevaporator and a second evaporator allows the intra-compartmenttemperature difference between a cold storage compartment and a freezercompartment to be realized efficiently. A reduction in temperaturedifference between the cold storage compartment temperature and theevaporation temperature of the first evaporator enables the temperaturevariation and dehumidifying action inside the cold storage compartmentto be suppressed.

By controlling the amount of throttling of a refrigerant flow rateadjustable unit to reduce the difference between the evaporationtemperature of each respective evaporator and the intra-compartmenttemperature of each respective cooling compartment to 5° C. or less, thetemperature variation and dryness inside the cooling compartment can befurther suppressed. Also, the efficiency of refrigeration cycle can befurther enhanced.

By controlling the evaporation temperature of the first evaporatorwithin a range of −5° C. to 5° C., the difference between the coldstorage compartment temperature and the evaporation temperature of thefirst evaporator is further reduced, thereby allowing the temperaturevariation and dehumidifying action of the cold storage compartment to befurther suppressed.

By installing a refrigerant flow rate adjustable unit in a freezertemperature compartment, the forming of frost on an electric expansionvalve is reduced, thereby allowing the defrosting of the electricexpansion valve to be facilitated.

When the freezer temperature compartment is cooled down quickly, theamount of throttling of the refrigerant flow rate adjustable unit isreduced and the evaporation temperature of the second evaporator islowered, thereby lowering the temperature of cold air supplied to thefreezer compartment and accelerating the refrigeration speed of foodsand the like. As a result, the effect of rapid refrigeration isincreased and the refrigeration storage quality of foods is enhanced.

What is claimed is:
 1. A refrigerating unit comprising: (a) compressor; (b) condenser; (c) a plurality of evaporators connected in series; (d) a capillary tube disposed between said condenser and each of said plurality of evaporators; (e) a coolant flow rate adjustable unit disposed between respective evaporators of said plurality of evaporators; (f) a bypass circuit bypassing it least one evaporator of said plurality of evaporators; and (g) a coolant, wherein said bypass circuit is disposed in parallel with said at least one evaporator and said coolant flow rate adjustable unit, said compressor, condenser, evaporator, capillary tube, coolant flow rate adjustable unit, bypass circuit and coolant constitute a refrigeration cycle, said coolant circulates in said refrigeration cycle, said coolant flow rate adjustable unit controls variably respective evaporation temperatures of said plurality of evaporators, and when cooling of said at least one evaporator disposed in parallel with said bypass circuit is not needed, said coolant flow rate adjustable unit is totally closed, thereby allowing said coolant to be channeled to said bypass circuit only.
 2. The refrigerating according to claim 1, wherein said plurality of evaporators include a first evaporator and a second evaporator, said coolant flow rate adjustable unit is disposed between said first evaporator and said second evaporator, said capillary tube has a first capillary tube and a second capillary tube, said first capillary tube is disposed between said condenser and said first evaporator, said bypass circuit has a branch connection unit, said second capillary tube and a merging connection unit, and said coolant flowing from said first capillary tube flows bybreaking into two flows at said branch connection wilt, one flowing in said first evaporator and another flowing in said bypass circuit, and said two flows merge at said merging connection unit to get to said second evaporator.
 3. The refrigerating unit according to claim 1, wherein said coolant flow rate adjustable unit is totally closed when said at least one evaporator disposed in parallel with said bypass circuit is defrosted under an off cycle state.
 4. A refrigerating unit comprising: (a) a compressor; (b) a condenser; (c) a first evaporator and a second evaporator connected in series; (d) a coolant flow rate adjustable unit with a function of totally closing disposed between said first evaporator and said second evaporator; (e) a capillary tube disposed between said condenser and said first evaporator; and (f) a bypass circuit bypassing said first evaporator and said coolant flow rate adjustable unit, wherein said compressor, condenser, first evaporator, second evaporator, coolant flow rate adjustable unit, capillary tube, bypass circuit and coolant constitute a refrigeration cycle, said coolant flow raw adjustable unit controls a flow rate of said coolant such that a first evaporation temperature of said first evaporator is made higher than a second evaporation temperature or said second evaporator, and, when cooling of said at least one evaporator disposed in parallel with said bypass circuit is not needed, said coolant flow rate adjustable unit is totally closed, thereby allowing said coolant to be channeled to said bypass circuit only.
 5. The refrigerating unit according to claim 4, wherein said coolant flow rate adjustable unit is totally closed when said at least one evaporator disposed in parallel with said bypass circuit is defrosted under an off cycle state.
 6. A refrigerator comprising a plurality of cooling compartments and said refrigerating unit according to claim 1, wherein respective cooling compartments of said plurality of cooling compartments are set to temperatures that are different from one another, said each respective evaporator is installed in each respective cooling compartment of said plurality of cooling compartments, said refrigerant flow rate adjustable unit controls a flow rate of said refrigerant such that an evaporation temperature of said each respective evaporator located at an upstream side of said refrigeration cycle is made higher than an evaporation temperature of said each respective evaporator located at a downstream side thereof, and said each respective evaporator located at an upstream side of said refrigeration cycle is installed in respective cooling compartments, each being set to a higher temperature in succession.
 7. A refrigerator comprising a plurality of cooling compartments and said refrigerating unit according to claim 4, wherein said plurality of cooling compartments include a cold storage temperature compartment and a freezer temperature compartment, said first evaporator is installed in said cold storage temperature compartment; and said second evaporator is installed in said freezer temperature compartment.
 8. A refrigerator comprising a plurality of cooling compartments and said refrigerating unit according to claim 5, wherein said plurality of cooling compartments include a cold storage temperature compartment and a freezer temperature compartment, said first evaporator is installed in said cold storage temperature compartment, and said second evaporator is installed in said freezer temperature compartment.
 9. The refrigerator according to claim 6, wherein said refrigerant flow rate adjustable unit controls a flow rate of said refrigerant such that a difference in temperature between an interior of said each respective cooling compartment and said each respective evaporator installed in said each respective cooling compartment is 5° C. or less.
 10. The refrigerator according to claim 7, wherein an evaporation temperature of said first evaporator is controlled such that an evaporation temperature of said first evaporator ranges from −5° C. to 5° C.
 11. The refrigerator according to claim 7, wherein said refrigerant flow rate adjustable unit is installed in said freezer temperature compartment.
 12. The refrigerator according to claim 7, wherein, when said freezer temperature compartment is rapidly cooled down, said second evaporation temperature of said second evaporator is made lower than said first evaporation temperature of said first evaporator by reducing an extent of throttling of said refrigerant flow rate adjustable unit.
 13. The refrigerator according to claim 7, wherein said refrigerant flow rate adjustable unit controls a flow rate of said refrigerant such that a difference in temperature between an interior of said each respective cooling compartment and said each respective evaporator installed in said each respective cooling compartment 5° C. or less.
 14. The refrigerator according to claim 7, wherein an evaporation temperature of said first evaporator is controlled such that an evaporation temperature of said first evaporator ranges from −5° C. to 5° C.
 15. The refrigerator according to claim 8, wherein said refrigerant flow rate adjustable unit is installed in said freezer temperature compartment.
 16. The refrigerator according to claim 8, wherein, when said freezer temperature compartment is rapidly cooled down, said second evaporation temperature of said second evaporator is made lower than said first evaporation temperature of said first evaporator by reducing an extent of throttling of said refrigerant flow rate adjustable unit.
 17. The refrigerating unit according to claim 2, wherein said coolant flow rate adjustable unit is totally closed when said at least one evaporator disposed in parallel with said bypass circuit is defrosted under an off cycle state. 